router startup behavior
mborchers at splitrock.net
Wed Jan 16 14:48:51 UTC 2002
> > Just guessing - you're seeing these events between midnight
> > and 5 am?
> Hm, couldn't reist this one: "which time zone"?
> Just hinting that even though it's that time interval in the US, local
> time is different in other places around the world, so if this is
> causing disturbance, others are probably being hit in their working
Heh, the "perpetual global maintenance window syndrome", eh? A
very useful concept...
> Besides, I was under the impression that to activate a new outbound
> roting policy on a Cisco, you could just modify / replace it, but that
> you would still have to do
> router#clear ip bgp xxx soft out
> to activate it. This means that the policy for an existing peer can
> be modified without having to remove the peering and reenable it
> shortly thereafter (something which would cause needless route
Somewhat true. The new policy would not be applied to routes that
were already in the table, but would be applied to any adds/withdrawals
that occur once the policy changes are placed in the configuration.
This fact has a synergistic effect when you're making changes that
affect lots of sessions. So a policy change made a significant time
before a clear or soft clear could in fact result in flaps.
Also consider: there are a lot of routers using traditional ACL's in their
policies (as opposed to things like prefix-lists which have more granular
editing features) which would necessitate removing the ACL completely and
rewriting it with updated lines. Due to the above, a potential for leaks
exists unless the session is either shutdown or deleted while acl's are
If the sequence of events in a configuration script is not well thought
out, the result could be what Ratul has observed in his study.
> - Håvard
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